As I travel abroad a lot, I usually tip about 10% of the restaurant bill. My Parisian friends are horrified. They agree that 10% is about right, but they do cap it around EUR 10 ! For our last dinner together in Paris, the price for 3 was about EUR 250 in a really nice restaurant with really nice service. They would have given EUR 5 for a tip and barely accepted that I go all the way up to EUR 10 (plus an additional EUR 10 for the voiturier )